Boxes containing the means necessary for connecting cables to equipment and disposed in determined positions along such cables are conventionally designed to be sealed, in particular when they are to be mounted outdoors or underground. It is advantageous to preserve, as much as possible, continuity of the electrical and/or optical conductors of a cable on which tapping is performed for connecting equipment. Sealed boxes have therefore been developed that enable a cable to pass through them via two openings provided in two different walls of the same box, or, alternatively, that enable a cable folded over to form a U-loop to pass through a single opening.
In a box designed to enable a cable to pass through it, the two openings required for the cable to pass through the box are generally situated at a join zone between two dissociable portions of the box, e.g. in the form of recesses opening out into the zone on which a lid bears against a box shell.
It is then possible to insert a cable transversely into the recesses, without it being necessary to thread one end of the cable through an orifice, which is unacceptable whenever there is a long length of cable to be threaded.
Implementing a sealed box provided with a cable passageway opening out into a join zone between the box portions involves implementing means for providing sealing in the zone in which the cable meets the two box portions.
As is known, it is difficult to obtain and to sustain sealing of that type, referred to as three-point sealing, between the elements constituted by a cable and by two touching box portions because of the necessary co-operation between elements, e.g. by alignment, in particular if the box is re-opened subsequently.
Document U.S. Pat. No. 5,235,134 describes a box enabling a cable folded over to form a U-loop to pass into it such that the two cable portions situated on either side of the fold come out side-by-side from the same side of the box. A hollow tubular body makes it possible for the U-looped cable to pass through, and its base is closed off by a sealing gasket provided with individual through holes for the two portions of the folded-over cable and for branch cables. The gasket is compressed against the tubular body and against the cables by means of a compression assembly formed of two portions clamped firstly against each other and secondly against the body by means of screws. The top of the tubular body receives a cylindrical cap mounted in sealed manner over the U-loop of the cable, and over the branches established at that level. That box, which is circular or oval in section has the characteristic of making provision to pass all of the cables, looped or non-looped, via individual holes in a common circular or oval gasket whose dimensions must remain small for physical reasons. Such a box can therefore be unsuitable when the looped cable is an optical cable which has a minimum radius of curvature that is quite large. In addition, by design, that type of box is ill-suited to receiving equipment modules such as, for example, optical tapping modules or cassettes that can be advantageously incorporated.